Influence of Support and Linker Parameters on the Activity of Silica-Supported Catalysts for Cyclic Carbonate Synthesis

Silica-supported, bimetallic aluminium(salen) complexes bearing pendant quaternary ammonium groups catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide in both batch and gas-phase flow reactors. The influence of particle and pore size of the silica support on catalyst activity was investigated with smaller particle sizes (<80 mu m) being advantageous to catalyst activity, whereas the silica pore size had little effect on catalyst activity. The nature of the silica support also affected catalyst stability and the Fluorochem LC301 silica gave a catalyst with both the highest intrinsic activity and the lowest rate of deactivation. The catalysts are attached to the silica through a linker containing three or eleven carbon atoms. The longer linker was found give a catalyst loading three times higher than the shorter linker, but this was offset by a three times lower activity for the catalyst with the longer linker.